Simulation of LS -al command in C language

C The code is as follows ：

#include <stdio.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <pwd.h>
#include <grp.h>
#include <time.h>
#include <string.h>

//  Simulation Implementation ls -al command 
// -rwxrwxrwx 1 x x 12 Feb 10 18:49 1.txt
int main(int argc, char* argv[]) {
    
    if (argc < 2) {
    
       printf("usage:\n\t %s filename\n", argv[0]);
       return -1;
    }

    //  adopt stat Function to get the information of the file passed in by the user 
    struct stat st;
    int ret = stat(argv[1], &st);
    if (ret == -1) {
    
        perror("stat");
        return -1;
    }
    
    //  Get file type and file permissions , altogether 10 position 
    // perms String array is used to save file types and permissions 
    char perms[11] = {
    0};

    // S_IFMT It's a mask , And it can get the file type 
    switch (st.st_mode & S_IFMT) {
    
        //  A symbolic link 
        case S_IFLNK:
            perms[0] = 'l';
            break;
        //  Catalog 
        case S_IFDIR:
            perms[0] = 'd';
            break;
        //  Ordinary documents 
        case S_IFREG:
            perms[0] = '-';
            break;
        //  Block device 
        case S_IFBLK:
            perms[0] = 'b';
            break;
        //  Character device 
        case S_IFCHR:
            perms[0] = 'c';
            break;
        //  The Conduit 
        case S_IFIFO:
            perms[0] = 'p';
            break;
        //  Socket 
        case S_IFSOCK:
            perms[0] = 's';
            break;
        default:
            perms[0] = '?';
            break; 
    }

    //  Get the permission of the file 
    //  Get the file owner's read 、 Write 、 Executive authority 
    perms[1] = st.st_mode & S_IRUSR ? 'r' : '-';
    perms[2] = st.st_mode & S_IWUSR ? 'w' : '-';
    perms[3] = st.st_mode & S_IXUSR ? 'x' : '-';
    
    //  Get the read of the group to which the file belongs 、 Write 、 Executive authority 
    perms[4] = st.st_mode & S_IRGRP ? 'r' : '-';
    perms[5] = st.st_mode & S_IWGRP ? 'w' : '-';
    perms[6] = st.st_mode & S_IXGRP ? 'x' : '-';
    
    //  Get others to read the file 、 Write 、 Executive authority 
    perms[7] = st.st_mode & S_IROTH ? 'r' : '-';
    perms[8] = st.st_mode & S_IWOTH ? 'w' : '-';
    perms[9] = st.st_mode & S_IXOTH ? 'x' : '-';
    
    //  Get the number of hard links 
    int link_num = st.st_nlink;

    //  File owner 
    char* file_user = getpwuid(st.st_uid)->pw_name;

    //  File group 
    char* file_group = getgrgid(st.st_gid)->gr_name;

    //  Get file size 
    long int file_size = st.st_size; 

    //  Get modification time 
    char* temp_file_time = ctime(&st.st_mtime);

    //  Remove the newline character in the time string 
    char file_time[512] = {
    0};
    strncpy(file_time, temp_file_time, strlen(temp_file_time) - 1);

    char buf[1024];
    sprintf(buf, "%s %d %s %s %ld %s %s", perms, link_num, file_user, file_group, file_size, file_time, argv[1]);

    printf("%s\n", buf);

    return 0;
}

effect ：

[email protected]:/mnt/c/Users/x/Pictures/code/lesson12$ gcc ls-l.c -o ll
[email protected]:/mnt/c/Users/x/Pictures/code/lesson12$ ./ll 1.txt
-rwxrwxrwx 1 x x 12 Thu Feb 10 18:49:38 2022 1.txt